From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=59781 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Ou3UD-0000h5-Ox for qemu-devel@nongnu.org; Fri, 10 Sep 2010 09:17:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1Ou3TR-0001re-Hu for qemu-devel@nongnu.org; Fri, 10 Sep 2010 09:17:02 -0400 Received: from mail-gy0-f173.google.com ([209.85.160.173]:34614) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1Ou3TR-0001rY-Bh for qemu-devel@nongnu.org; Fri, 10 Sep 2010 09:17:01 -0400 Received: by gya1 with SMTP id 1so1312317gya.4 for ; Fri, 10 Sep 2010 06:17:00 -0700 (PDT) Message-ID: <4C8A2FC6.8080902@codemonkey.ws> Date: Fri, 10 Sep 2010 08:16:54 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format References: <1283767478-16740-1-git-send-email-stefanha@linux.vnet.ibm.com> <4C84E738.3020802@codemonkey.ws> <4C865187.6090508@redhat.com> <4C865CFE.7010508@codemonkey.ws> <4C8663C4.1090508@redhat.com> <4C866773.2030103@codemonkey.ws> <4C86BC6B.5010809@codemonkey.ws> <4C874812.9090807@redhat.com> <4C87860A.3060904@codemonkey.ws> <4C888287.8020209@redhat.com> <4C88D7CC.5000806@codemonkey.ws> <4C8A1311.8070903@redhat.com> <4C8A15C4.40201@redhat.com> In-Reply-To: <4C8A15C4.40201@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Avi Kivity Cc: Kevin Wolf , Stefan Hajnoczi , qemu-devel@nongnu.org On 09/10/2010 06:25 AM, Avi Kivity wrote: > On 09/10/2010 02:14 PM, Avi Kivity wrote: >> >>> >>> qcow2 is not a properly designed image format. It was a weekend >>> hacking session from Fabrice that he dropped in the code base and >>> never really finished doing what he originally intended. The >>> improvements that have been made to it are almost at the heroic >>> level but we're only hurting our users by not moving on to something >>> better. >>> >> >> I don't like qcow2 either. But from a performance perspective, it >> can be made equivalent to qed with some effort. It is worthwhile to >> expend that effort rather than push the burden to users. > > btw, despite being not properly designed, qcow2 is able to support > TRIM. qed isn't able to, except by leaking clusters on shutdown. > TRIM support is required unless you're okay with the image growing > until it is no longer sparse (the lack of TRIM support in guests make > sparse image formats somewhat of a joke, but nobody seems to notice). It's actually pretty easy in QED and it should perform very well. http://wiki.qemu.org/Features/QED/Trim Regards, Anthony Liguori